Production of human chorionic gonadotropins has been reported not only in trophoblastic neoplasms but rarely in carcinomas arising in extragenital sites such as lung and urinary bladder. HCG production has not been known to occur in endometrial carcinoma. We are in the process of studying HCG production by this type of cancer by immunohistologic techniques, and correlate it with determinations of HCG in serum. The finding of this choriocarcinomatous element in endometrial cancer has significant therapeutic and prognostic significance.